Sample supporting means for high-temperature x-ray diffractometer

ABSTRACT

In a diffractometer where a sample carrier is in the form of a strip or wire spanned between two electrodes for resistance heating of the carrier, one of the electrodes is placed under a torsional bias to accommodate thermal expansion of the carrier by a winding of added length of carrier onto the torsionally biased electrode.

Unite States atet Inventor Appl. No.

Filed Patented Assignee Priority Constantin Politis Hoclistetten, Germany May 8, 1969 Nov. 9, 1971 Gesellschaft fur Kernforschung m.b.H. Karlsruhe, Germany May 8, 1968 Germany SAMPLE SUPPORTING MEANS FOR HIGH- TEMPERATURE X-RAY DIFFRACTOMETER 5 Claims, 2 Drawing Figs.

U.S. Cl.....

Field of Search 250/5l.5 G0ln 23/20 250/41.9 SE, 49.5 B, 51.5; 313/278 [56] References Cited UNITED STATES PATENTS 2,656,480 10/1953 Corbell et a1. 313/278 3,005,099 10/1961 Fournier et al. 250/51.5 FOREIGN PATENTS 975,259 10/1961 Germany 250/51.5

OTHER REFERENCES High Temperature, High Vacuum, Diffractometer Attachment" by J. lntrater et al., from The Review of Scientific Instruments, Vol. 32, No. 8, August, 1961, pages 905 & 906.

Primary ExaminerWilliam F. Lindquist Attorney-Spencer & Kaye ABSTRACT: In a difi'ractometer where a sample carrier is in the form of a strip or wire spanned between two electrodes for resistance heating of the carrier, one of the electrodes is placed under a torsional bias to accommodate thermal expansion of the carrier by a winding of added length of carrier onto the torsionally biased electrode.

SAMPLE SUPPORTING MEANS FOR HIGH- TEMPERATURE X-RAY DIFFRACTOMETER The invention relates to a highJemperature X-ray diffractometer consisting of pressure and, respectively, high-vacuum resistant measurement chamber with a window permeable to X-rays and arranged on the circumference of the chamber and a resistance-heated strip or wire of high-temperature metals as the sample holder attached at window level between two water-cooled electrodes.

In the high-temperature investigations carried out up to 3,000 C. and above the thennal expansion of the sample carrier on which the focusing point has been adjusted at room temperature has a particularly disturbing influence. To compensate for the thermal expansion of the sample carrier during measurement, it was necessary in the devices known so far to adjust the focusing point. This required very complex technically expensive adjusting mechanisms on the measurement device. In addition, such adjustment, which was not always simple, needed a certain skill of the operating personnel.

It is also known that specially shaped sample carriers can be used which can compensate for the thermal expansion and contraction respectively, during measurement. These sample carriers are very expensive and yet do not work reliably.

Hence, it was the objective of the invention to remove the disadvantages of known devices and replace them by as simple a device as possible which makes it possible to maintain throughout the entire measurement a focusing point of the X- ray beam set at the beginning of the measurement on a resistance-heated metal strip or wire acting as the sample carrier or the sample proper.

This problem is solved in the invention by fixing the resistance-heated metal strip or wire, which acts as the sample carrier or as the sample proper, between the two electrodes in such a way as to subject it to a continuous tensile stress. At least one side of the sample carrier or the sample, respectively, is threaded into an electrode which is slotted at the fixing end, and wound at least partly on the electrode circumference in a direction opposite that of the torsional stress. The partial winding of the sample carrier on the rod-shaped electrode and the prestressing make for a good electrical contact between the electrode and the sample carrier which at the same time acts as the heating conductor. According to the invention the electrode under torsional stress is carried through the wall of measurement chamber so as to be rotatable, vacuum and pressuretight, respectively. The element causing torsional stress is set up outside the measurement chamber and thus can be exchanged easily for an element producing harder or softer torsional stresses. Moreover, it is not damaged by the high temperatures prevailing within the measurement chamber. As such an element generating torsional stress the invention contains a tension or compression spring hinged to a lever attached perpendicular to the axis of rotation of the electrode. Alternatively, this torsional stress generating element can be also a spring clip acting on a lever which is attached perpendicular to the axis of rotation of the electrode.

A further improvement of the high-temperature X-ray diffractometer is achieved in the invention by making replaceable the window which is permeable to X-rays. In this way, it is possible to use different window foils adapted to the specific purpose of the measurement. The beryllium window usually employed in such equipment is replaced at advantage, e.g., by a nickel window in investigations under a high-vacuum atmosphere.

Below, the invention will be explained in more detail on the basis of a drawing. In this drawing, FIG. 1 is a sectional view of the X-ray diffractometer device according to the invention, and FIG. 2 is a partially sectional top view of the device shown in FIG. 1.

The high-temperature X-ray diffractometer device according to the invention consists of a flat-bottomed cylindrical brass pot 2 equipped with a cooling jacket 1 and having welded-on flange 3 to which the flat lid 5 equipped with a centering collar 4 is secured by means of three flange bolts 6. The sealing action against vacuum and pressure, respectively, is

provided by a rubber O-ring 8 inserted in a groove 7 in the vessel flange 3. A slot-shaped X-ray beam inlet and outlet window 9 comprising an arc angle of is provided for in the bottom section of the cylindrical vessel. The counterframe 11 with the window foil 12 of 20 pm nickel sheet soldered to it is attached by bolts 13 to the window frame 10 which penetrates through the cylindrical brass pot 2 and the cooling jacket 1. In this way, the counterframe 11 with the window foil 12 soldered to it can be replaced any time by a different frame with a different type of foil. The vacuum seal of the window is produced by a flat seal 14. The cooling jacket 1 has a coolant inlet pipe 16. Two rod-shaped water-cooled hollow electrodes 17, 18 made of VZA-grade steel penetrate through the flat lid 5, their upper ends are slotted to hold the current feed lines. The electrodes can be made just as well of copper or any other electrode material. In the electrode 18 shown in a sectional view the arrangement of the cooling water inlet pipe 19 and outlet pipe 20 can be seen. Both electrodes 17, 18 are provided with a slot at the bottom to hold the sample carrier 21. The sample carrier is held in the firmly fixed condition by one setscrew 22 each. The centrally arranged sample carrier 2l'at the same time acting as the heating conductor with the sample preferably sintered on (not shown) is arranged at the level of the X-ray beam inlet and outlet window 9. In order to have the heat generated by the heat conductor-sample carrier 11 flow into the sample as completely as possible, said sample carrier 21 is surrounded bypackages of heat conduction baffles of brightly polished tungsten or molybdenum sheet: one baffle package 23 is arranged parallel to the bottom of the pot and consists of three circular baffle disks which become larger towards the bottom and are drawn on three spacer pins 24 which, in turn, fit into centering bores 25 in the bottom of the pot; one package 26 shielding the sample against the sidewalls of the pot consists of concentric baffle cylinders with a slotshaped recess 27 fitting into each area of the slot-shaped window 9 and resting on the bottom of the pot and on the disks of baffle package 23, respectively; and bafi'le package 28 shields against the lid 5 and rests upon the coaxial cylinder package 26 in which the distance between the baffles X is maintained by spacer pins 29 and in which each baffle has a recess 30 for penetration of the electrode pair 17, 18 with the sample carrier 21 already fixed; the latter baffle package 28 in addition features circular holes 32 arranged on the axis between the sample and the sight glass 31 (FIG. 2) so that observation of the sample is possible also during setting and during the measurement. A correct introduction of the electrodes 17, 18 into the bafile package and into the right position relative to the X- ray beam inlet and outlet window 9 is achieved by two centering pins 33 staggered at 180. The sample carrier 21 is kept under a continuous tensile stress as a result of the fact that the electrode 18 led through the lid 5 so as to be rotatable is turned always in the direction of winding (Figure 2) by means of tension spring 36 which is arranged above the lid 5 and acts upon a lever 34 rigidly connected with the electrode 18 and hooked into the bolt 35. The rotatable and yet pressure and vacuum-tight penetration of the electrode 18 through the flat lid 5 is achieved by one rubber O-ring 37, 38 each arranged inside and outside the lid, each of them firmly pressed by the cap screws 39, 40 into the bevels of the guide sleeve 41 welded to the lid 5. The guide sleeve 41 is welded into the lid 5. Electrode 17 cannot be rotated and penetrates through the lid 5, which is at the potential of electrode 18, by means of an electrically insulating Teflon ring 42. The cap screw 43 which attaches to the collar 44 of electrode 17 provides for a finn seat of the electrode. The seal against vacuum or overpressure in the interior of the pot is achieved by the rubber O-rings 45 and 46. For operation in a foreign gas atmosphere there is a gas inlet pipe 47 in the lid 5 (FIG. 2). There is no need for a gas outlet pipe, since more recently there has been an increasing tendency to carry out the measurements in a quiescent atmosphere; however, if need be, such pipe could be attached to the lid 5 any time.

it will be noted from the figures that the threading of sample carrier 21 into slots in the electrodes and the particular positioning of set screws 22 means that the sample carrier is accessible for X-ray beam impingement and reflection over the entire 180 of the window 9.

It is within the framework of the invention that also different elements causing prestressing of the sample carrier can be used than those described in the example above. In particular, it is possible, to use packing seals instead of rubber O-ring seals. Moreover, it is possible to attach the counterframe 11 carrying the window foil 12 directly to the cylindrical housing, e.g. to the cooling jacket 1.

The device according to the invention permits the rapid and safe performance of experiments up to 3,000 C. and above. Work can be carried out in the high vacuum up to 1X10 torr as well as under pressure. It is possible also to work under nitrogen, hydrogen, inert gas or any atmosphere with the invention.

We claim:

1. In a high-temperature X-ray diffractometer comprising a pressure and high-vacuum tight measurement chamber having a cylindrical section, an X-ray permeable window arranged on the circumference of said section of said chamber, two watercooled electrodes supported in said chamber, and a resistance-heated strip or wire made of high-temperature metal fastened at window level between said two water-cooled electrodes and adapted either to be, or to support and heat, a test sample, the electrical path being from a first of said electrodes, through said strip or wire, to the second of said electrodes, the improvement that the strip or wire is threaded into a slot in a one of said electrodes having a cylindrical section in said chamber, that the strip or wire is at least partially wound on the circumference of said section of said one of said electrodes, that said one of said electrodes is rotatably mounted in and extends through a wall of the measurement chamber, that there is provided means for making the point at which said one of said one of said electrodes passes through said wall vacuum and pressure-tight, and that there is provided outside said chamber means for generating a torsional stress on said one of said electrodes, the direction of the torsional stress tending to wind said strip or wire further onto said one of said electrodes, whereby .said strip or wire is kept under a continuous tensile stress and it is possible to maintain throughout an entire measurement up to 3,000 C. a focusing point of an X-ray beam set at the beginning of the measurement of said strip or wire.

2. in a diffractometer as claimed in claim I, the further improvement that the means for generating the torsional stress comprises a spring attached at one end to said chamber and hinged at its other end on a lever attached to said one of said electrodes perpendicularly to the axis of rotation of said one of said electrodes.

3. In a diffractometer as claimed in claim I, the further improvement that the means for generating the torsional stress comprises a spring clip attached at one end to said chamber and at its other end to a lever connected to said one of said electrodes perpendicularly to the axis of rotation of said one of said electrodes.

4. in a diffractometer as claimed in claim 1, the further improvement that there is provided means for rendering said window replaceable.

5. In a diffractometer as claimed in claim 1, the further improvement that said strip or wire is accessible for X-ray beam impingement and reflection over 180".

* a a s a: 

1. In a high-temperature X-ray diffractometer comprising a pressure and high-vacuum tight measurement chamber having a cylindrical section, an X-ray permeable window arranged on the circumference of said section of said chamber, two water-cooled electrodes supported in said chamber, and a resistance-heated strip or wire made of high-temperature metal fastened at window level between said two water-cooled electrodes and adapted either to be, or to support and heat, a test sample, the electrical path being from a first of said electrodes, through said strip or wire, to the second of said electrodes, the improvement that the strip or wire is threaded into a slot in a one of said electrodes having a cylindrical section in said chamber, that the strip or wire is at least partially wound on the circumference of said section of said one of said electrodes, that said one of said electrodes is rotatably mounted in and extends through a wall of the measurement chamber, that there is provided means for making the point at which said one of said one of said electrodes passes through said wall vacuum and pressure-tight, and that there is provided outside said chamber means for generating a torsionaL stress on said one of said electrodes, the direction of the torsional stress tending to wind said strip or wire further onto said one of said electrodes, whereby said strip or wire is kept under a continuous tensile stress and it is possible to maintain throughout an entire measurement up to 3,000* C. a focusing point of an X-ray beam set at the beginning of the measurement of said strip or wire.
 2. In a diffractometer as claimed in claim 1, the further improvement that the means for generating the torsional stress comprises a spring attached at one end to said chamber and hinged at its other end on a lever attached to said one of said electrodes perpendicularly to the axis of rotation of said one of said electrodes.
 3. In a diffractometer as claimed in claim 1, the further improvement that the means for generating the torsional stress comprises a spring clip attached at one end to said chamber and at its other end to a lever connected to said one of said electrodes perpendicularly to the axis of rotation of said one of said electrodes.
 4. In a diffractometer as claimed in claim 1, the further improvement that there is provided means for rendering said window replaceable.
 5. In a diffractometer as claimed in claim 1, the further improvement that said strip or wire is accessible for X-ray beam impingement and reflection over 180*. 